Ascorbic acid and its derivatives are known as compounds exhibiting efficacy and effects in whitening action, anti-oxidant action, collagen synthesis promotion action, etc., and they are added to medicines, cosmetics, feeds and the like.
Of the ascorbic acid derivatives, compounds wherein a hydroxyl group at the 2-position is esterified with phosphoric acid and a hydroxyl group at the 6-position is esterified with a higher fatty acid and their salts are hardly oxidized and are stable and amphipathic. On that account, these compounds have high affinity for living organisms and rapidly penetrate into the organism tissues such as the skin, so that application of the compounds to medicines, cosmetics, feeds, etc. is expected.
However, when skin external preparations are prepared from the salts of higher fatty acid esters of ascorbic acid-2-phosphoric acid ester, decomposition of the salts takes place in the preparations, and there occurs a problem that their effects are not sufficiently obtained.
As means to obtain a stable emulsion, an emulsified cosmetic comprising an ascorbic acid-phosphoric acid ester salt, a specific surface active agent and an oil agent has been disclosed in the past in, for example, a patent document 1, and an emulsified cosmetic comprising specific two kinds of polyglycerin fatty acid esters, lecithin and an oil component has been disclosed in the past in, for example, a patent document 2.
In any of the means disclosed in the above documents, however, it is difficult to stably emulsify the salt of a higher fatty acid ester of ascorbic acid-2-phosphoric acid ester.
Further, the present inventors have already proposed a skin external preparation and a cosmetic each of which comprises a salt of a higher fatty acid ester of ascorbic acid-2-phosphoric acid ester, an oil component, a surface active agent, water and a higher alcohol and has excellent stability (patent document 3).
The cosmetic of the patent document 3, however, is white, and any cosmetic having a transparent to translucent beautiful appearance has not been obtained yet.
Patent document 1: Japanese Patent Laid-Open Publication No. 256173/2000
Patent document 2: WO 2002/078650
Patent document 3: Japanese Patent Laid-Open Publication No. 187465/2005